Synergistic partnership between Serratia marcescens 2G5 and Amorpha fruticosa L. for enhanced phytoremediation of lead and cadmium contaminated soil

Cadmium (Cd) and lead (Pb) contamination in soils pose a serious environmental challenge requiring urgent remediation. This study aimed to evaluate the efficiency of Serratia marcescens 2G5 and Amorpha fruticosa L. in the synergistic remediation of heavy metal-contamination in soil, and to investigate the effect of 2G5 inoculation on the bioaccumulation and translocation of Pb and Cd in A. fruticosa L. and the rhizosphere soil microbiomes. The results showed that 2G5 inoculation mitigated the negative impacts of Cd and Pb stress on A. fruticosa L., increasing total plant biomass by 22.19 % and enhancing the phytoextraction efficiency of Cd and Pb by 64.18-102.87 %. The positive effects of 2G5 inoculation on the growth and soil remediation of A. fruticosa L. were probably attributed to the significant improvements in soil enzyme activities (urease, acid phosphatase, catalase, and sucrase) and soil nutrient contents [Total phosphorus (TP), available phosphorus (AP) and hydrolyzed nitrogen (AN)]. Principal co-ordinate analysis revealed that both heavy metal contamination and 2G5 inoculation significantly influenced the bacterial community structure in the rhizosphere soil, with the influence of heavy metals being greater than that of the inoculation. Patescibacteria (27.02 %-30.12 %) have replaced Proteobacteria (22.38-24.02 %) as the dominant phyla in contaminated soil. The Mantel test results indicated that soil heavy metals, along with AP and urease, were the primary environmental factors influencing the bacterial community at the phylum level under heavy metal contamination. Furthermore, linear discriminant analysis effect size (LEfSe) identified Ellin6067 (Nitrosomonadaceae) and Dongia (Rhodospirillaceae) as the key bioindicators of heavy metal contamination and Sphingomonas and Micropepsis as the key bioindicators of 2G5 inoculation. In conclusion, the findings of this study revealed the potential and feasibility of combining S. marcescens 2G5 and A. fruticosa L. for the remediation of soil heavy metal- contamination, offering a viable strategy for microbial agents and plants to cooperate in mitigating heavy metal contamination in soil.